Characterization of laser induced plasmas by optical emission spectroscopy: A review of experiments and methods

Advances in characterization of laser induced plasmas by optical emission spectroscopy are reviewed in this article. The review is focused on the progress achieved in the determination of the physical parameters characteristic of the plasma, such as electron density, temperature and densities of atoms and ions. The experimental issues important for characterization by optical emission spectroscopy, as well as the different measurement methods are discussed. The main assumptions of the methods, namely the optical thin emission of spectral lines and the existence of local thermodynamic equilibrium in the plasma are evaluated. For dense and inhomogeneous sources of radiation such as laser induced plasmas, the characterization methods are classified in terms of the optical depth and the spatial resolution of the emission used for the measurements. The review deals firstly with optically thin spatially integrated measurements. Next, local measurements and characterization in not optically thin conditions are discussed. Two tables are included that provide reference to the works reporting measurements of electron density and temperature of laser induced plasmas generated with diverse samples.     

Determination of Vecuronium Bromide in Pharmaceuticals: Development, Validation and Comparative Study of HPLC and CZE Analytical Methods

Vecuronium bromide is a neuromuscular blocking agent used for anesthesia to induce skeletal muscle relaxation. HPLC and CZE analytical methods were developed and validated for the quantitative determination of vecuronium bromide. The HPLC method was achieved on an amino column (Luna 150 × 4.6 mm, 5 μm) using UV detection at 205 nm. The mobile phase was composed of acetonitrile:water containing 25.0 mmol L^?1 of sodium phosphate monobasic (50:50 v/v), pH 4.6 and flow rate of 1.0 mL min^?1. The CZE method was achieved on an uncoated fused-silica capillary (40.0 cm total length, 31.5 cm effective length and 50 μm i.d.) using indirect UV detection at 230 nm. The electrolyte comprised 1.0 mmol L^?1 of quinine sulfate dihydrate at pH 3.3 and 8.0% of acetonitrile. The results were used to compare both techniques. No significant differences were observed (p > 0.05).     

Repair of guanyl radicals in plasmid DNA by electron transfer is coupled to proton transfer

By using gamma-irradiation in the presence of thiocyanate ions, we have generated guanyl radicals in plasmid DNA. These can be detected by using an Escherichia coli base excision repair endonuclease to convert their stable end products to strand breaks. The yield of enzyme-sensitive sites is strongly attenuated by the presence of micromolar concentrations of one of a series of singly substituted phenols, and it is possible to derive bimolecular rate constants for the reduction of DNA guanyl radicals by these phenols. More strongly reducing phenols were found to react more rapidly. This electron-transfer reaction also involves a proton transfer. By comparing the expected energetics of the reaction with the observed rate constants, the electron transfer is found to be mechanistically coupled with the proton transfer.     

Chemical Bonding of Transition‐Metal Co13 Clusters with Graphene

We carried out density functional calculations to study the adsorption of Co₁₃ clusters on graphene. Several free isomers were deposited at different positions with respect to the hexagonal lattice nodes, allowing us to study even the hcp 2d isomer, which was recently obtained as the most stable one. Surprisingly, the Co₁₃ clusters attached to graphene prefer icosahedron‐like structures in which the low‐lying isomer is much distorted; in such structures, they are linked with more bonds than those reported in previous works. For any isomer, the most stable position binds to graphene by the Co atoms that can lose electrons. We find that the charge transfer between graphene and the clusters is small enough to conclude that the Co–graphene binding is not ionic‐like but chemical. Besides, the same order of stability among the different isomers on doped graphene is kept. These findings could also be of interest for magnetic clusters on graphenic nanostructures such as ribbons and nanotubes.